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D( x )
x^2-(13*x)+40 = 0
x^2-(13*x)+40 = 0
x^2-(13*x)+40 = 0
x^2-13*x+40 = 0
x^2-13*x+40 = 0
DELTA = (-13)^2-(1*4*40)
DELTA = 9
DELTA > 0
x = (9^(1/2)+13)/(1*2) or x = (13-9^(1/2))/(1*2)
x = 8 or x = 5
x in (-oo:5) U (5:8) U (8:+oo)
(8*x-6)/(x^2-(13*x)+40)+(1-(7*x))/(x^2-(13*x)+40) = 0
(8*x-6)/(x^2-13*x+40)+(1-7*x)/(x^2-13*x+40) = 0
x^2-13*x+40 = 0
x^2-13*x+40 = 0
x^2-13*x+40 = 0
DELTA = (-13)^2-(1*4*40)
DELTA = 9
DELTA > 0
x = (9^(1/2)+13)/(1*2) or x = (13-9^(1/2))/(1*2)
x = 8 or x = 5
(x-5)*(x-8) = 0
(8*x-6)/((x-5)*(x-8))+(1-7*x)/((x-5)*(x-8)) = 0
8*x-7*x-6+1 = 0
x-5 = 0
(x-5)/((x-5)*(x-8)) = 0
(x-5)/((x-5)*(x-8)) = 0 // * (x-5)*(x-8)
x-5 = 0
x-5 = 0 // + 5
x = 5
x in { 5}
x belongs to the empty set
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